Changes to the hull gave a more complete internal protection and allowed the larger ships to make the same speed with the same powerplant. While Dreadnought had bulkheads that protected only the magazines, the Bellerophons had complete bulkheads running longitudinally through the ship. The 12-pounder guns that had been added to Dreadnought for protection from torpedo boats were recognised as being insufficient and their secondary armament was made up of 4-inch (102 mm) guns. A mainmast added ahead of the aft funnel was still affected by the plume of the fore funnel and was not considered a success. These changes did require some compromises in the design resulting in thinner armour, reducing the belt armor from 11 to 10 inches (254 mm), and a reduced coal bunkerage, which limited the steaming endurance.

The Bellerophon '​s design was virtually identical to that of the preceding Dreadnought, with some minor improvements.[1] The tripod foremast, which on Dreadnought was behind the forward funnel, was positioned in front of the forward funnel so that lookouts stationed on the observation platform could be out of the smoke plume.[1] A second tripod mast was placed in front of the second funnel.[2]

The ships of the Bellerophon class were 160.3 m (526 ft) long. They had a beam of 25.2 m (83 ft), a draught of 8.3 m (27 ft), and normally displaced 18,800 tonnes with a maximum displacement of 22,102 tonnes.[3]

The Bellerophon class had the same propulsion design as the previous Dreadnought. The ships were powered by four-shaft Parsons turbines in 18 coal-fired boilers. The ships' powerplants delivered at a rated 23,000 shp.[4]

The Bellerophon '​s armament featured an improved second battery. Sixteen 4 in (10 cm) guns replaced the twenty-seven 3 in (7.6 cm) guns on Dreadnought. However, the main armament was the same having ten 12 in (30 cm) guns in five twin turrets.[3]